Automotive instrument clusters utilize a large number of telltale lamps for indicating conditions existing throughout the vehicle. In some applications twenty or more lamps are used. Miniature incandescent lamps are generally used for this purpose.
Due to demand for increased reliability in the automotive industry, manufacturers are tending to replace the incandescent lamps with electronic devices such as light emitting diodes (LEDs). LEDs usually require a resistor in series to limit current through the device; the limited current generates very little heat. The LEDs and their resistors are easily mounted to conventional hardboard printed circuits with ordinary handling equipment. On the other hand, mounting these devices to typical flexible printed circuits is more involved, more expensive, and creates a difficult service procedure.